In the recent development of cellular technology standards, in particular for long term evolution (LTE), it is considered that certain types of devices, so-called low-cost (LC) devices, in particular machine type communication (MTC) devices, are operating in conditions where they do not have the optimal transmission and reception conditions in relation to base nodes resp. eNodeBs of the cellular network they are operating in. This affects as prominent example metering devices in basements, but other types of devices in extreme conditions may also be affected.
Hence as part of the 3GPP Release 13 definition for such LC devices it was suggested the so-called enhanced coverage (EC) mode. This solves said issues by allowing communication that way that by many repetitive receptions of the same data packets the receiver aggregates sufficient power until the data packets can be reliably read from the receiver. As a precondition the wireless communication device and the base node need to agree upon registration of the wireless communication device at the base node that on both sides of the air interface the enhanced coverage mode is activated. A precondition for that is that the base node supports EC devices, otherwise they were barred on that base node. The enhanced coverage support is performed up to a certain coverage enhancement limit which is also indicated by the base node, i.e. corresponding to the maximum of repetitions and resources a base node would spend for a user to achieve a certain coverage enhancement depth.
With the new enhanced coverage mode compared to the normal coverage (NC) mode, which complements to the known operating mode of wireless communication devices with a base node, further operation means need to be adapted as well.
One of this means is the mobility management. As part of that a wireless communication device operated in idle mode regularly looks up if—in particular due to a change of its location—another base node might serve better the wireless communication device.
As part of the definition of the enhanced coverage mode it is foreseen that base nodes operating in normal coverage have a higher camping priority for a wireless communication device than those in enhanced coverage. This applies when signals from a base node operating in normal coverage mode are receivable at the wireless communication device in sufficient quality, that means the suitability criterion S for a normal coverage base node is met. Hence for that situation it is defined that the wireless communication device will execute a reselection to that normal coverage base node and continue operating in normal coverage with that base node. From a power consumption perspective this is generally advantageous, as operating in normal mode requires less receive/transmit operations as especially for enhanced coverage mode subsequent repetitions and corresponding average is a mean to achieve the required additional coverage enhancement. Nevertheless to unconditionally apply this rule is disadvantageous for wireless communication devices that are operating under permanent enhanced coverage condition, e.g. when operated stationary. When such a wireless communication device, e.g. an electricity metering device, once decided to operate with a enhanced coverage base node, this is because there was no normal coverage base node available. As the metering device is not expected to move, and the cellular network topology remains most likely stable, each search for a normal coverage base node is expected to be unsuccessful and consequently in vain.
In this case a continuous search for a normal coverage base node would drain out the power of the wireless communication device, and all envisaged power saving of this rule would not be realized.
It is therefore the goal of present invention to overcome the mentioned disadvantages and to propose a solution for an in terms of power consumption improved operation of the wireless communication unit in a cellular network in enhanced coverage.
Further alternative and advantageous solutions would, accordingly, be desirable in the art.